A New Biodegradable Antiscalant for Thermal Desalination Plants

Abstract

Antiscalants are applied in thermal desalination plants (multistage flash and multieffect desalination) to control alkaline and nonalkaline scale in brine when saturation indices are exceeded. Antiscalants currently used are usually based on organophosphonates or are polymeric in nature. These antiscalants are discharged into the sea via brine blowdown and remain in the environment for a long time. Some of these antiscalants bioaccumulate in living organisms or act as a food source for microbes. Data presented in this article show the biodegradability and bioaccumulation properties of a new phosphorus- and nitrogen-free antiscalant. Performance data show the new antiscalant controls scale in brines up to a concentration factor of 2 and temperatures to 120°C. Saturation indices of these brines were calculated and correlated with the dose level required to control scale deposition. In addition, a detection method has been developed to help thermal plant operators measure antiscalant in brine, allowing them to control the dosage level.